FORMATION OF THE SINGHBHUM CRATON: MAGMATIC AND TECTONIC SETTING OF ARCHEAN GRANITOIDS IN THE SOUTHEASTERN REGION OF THE SINGHBHUM CRATON

The Singhbhum Craton is one of five Archean nuclei comprising Peninsular India. It is a composite Archean block that includes the Older Metamorphic Group, the Older Metamorphic Tonalite Gneisses, the Singhbhum Granite, and the Iron Ore Group as its major units. The ages of these components range from ~3.5 to ~3.1 Ga, although overlapping ages and similar rock types confound their genetic relationships. Plutonic felsic rocks from the southeastern portion of the Singhbhum Craton nucleus (BK1: a foliated granite, KP1: a non-foliated granite, and SG14: a non-foliated tonalite) yield ages of 3294±7 Ma (KP1) and 3373±12 Ma (BK1) that coincide with a pulse of Singhbhum Granite emplacement at 3.27 to 3.33 Ga. Since Saha (1994), HREE patterns have been consistently reported as depleted for this pulse and flat for the ~3.1 Ga pulse, whereas LREE abundances are more variable. We report major and trace element data for our three samples from new locations and compare them to these previous works to characterize the Archean felsic plutonic history of the craton. The petrogenesis of Archean Tonalite-Trondhjemite-Granodiorite (TTG) melts is hypothesized by a variety of mechanisms, including melting of subducted MORB-like oceanic crust, subduction of oceanic plateaus, and melting of wet basalts at the base of oceanic plateaus (Nair and Chacko, 2008; Polat, 2012; Martin, 2014; Upadhyay, 2019). We note that REE patterns and tectonic discrimination diagrams from trace element ratios may further elucidate a magmatic and tectonic setting for these rocks.